Combustion controlling device and method

ABSTRACT

A flame detection adjusting portion adjusts a preset reference threshold value based on a sensor output indicating disturbance light obtained from a flame sensor before an ignition attempt in combustion equipment and outputs an obtained adjusted threshold value, and a combustion flame detecting portion detects a presence or an absence of a combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during combustion in the combustion equipment and an adjusted threshold value.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of and priority to Japanese Patent Application No. 2017-052495, filed on Mar. 17, 2017, the entire contents of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a combustion controlling technique that controls a combustion depending on the presence or absence of a flame detected according to a sensor output of a flame sensor.

BACKGROUND ART

Combustion equipment used in industrial furnaces, boilers, air conditioners, kitchen appliances, heat exchangers, and the like is provided with a flame sensor that detects a light quantity of a flame in a burner and outputs an electrical signal, detects a presence or an absence of a flame using a combustion controlling device based on the sensor output of this flame sensor and a preset threshold value, and controls a combustion based on the sensor according to the detection result.

Conventionally, such a combustion controlling device detects a presence or an absence of a flame based on so-called hysteresis characteristics in which the extinction of a flame is detected at a flame extinction detection level lower than the ignition detection level that is the sensor output during detection of ignition in order to suppress effects of output changes of a flame sensor due to fluctuations of a flame (see, for example, PTL 1 and the like).

CITATION LIST Patent Literature

[PTL 1] JP-B-7-15328

[PTL 2] Japanese Patent No. 3943478

SUMMARY

However, since a presence or an absence of a flame is detected by comparing the sensor output of the flame sensor with a threshold value in the related art described above, in an environment in which there is a pseudo flame having a light quantity equal to or higher than the flame extinction detection level and equal to or lower than the ignition detection level due to effects of disturbance light, such as outside light or stray light, even if a flame is extinguished after ignition, the sensor output of the flame sensor may not be reduced to the flame extinction detection level. Since flame extinction cannot be detected in such a case, fuel continues to be output after extinction and a very dangerous state may be entered.

There is a proposed technique for preventing disturbance light from entering the flame sensor by improving the burner structure to suppress effects of such disturbance (see, for example, PTL 2 or the like). However, since the measure against the problem depends on the equipment manufacturer, not all combustion devices surely take the measure described above. In addition, application of the burner structure described above significantly increases the cost for measures since a change to existing combustion equipment, such as an exchange of an existing burner, is necessary.

The invention addresses such a problem with an object of providing a combustion controlling technique capable of controlling combustion equipment safely with respect to disturbance light without changing existing combustion equipment.

To achieve the object described above, according to the invention, there is provided a combustion controlling device that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the combustion controlling device comprising a flame detection adjusting portion that adjusts a preset reference threshold value based on the sensor output indicating disturbance light obtained from the flame sensor before an ignition attempt in the combustion equipment and outputs an obtained adjusted threshold value; a combustion flame detecting portion that detects a presence or an absence of a combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during combustion in the combustion equipment and the adjusted threshold value; and a combustion controlling portion that controls a combustion in the combustion equipment based on a combustion flame detection result obtained by the combustion flame detecting portion.

In addition, in one example of the configuration of the combustion controlling device according to the invention, the flame detection adjusting portion calculates an adjustment value indicating the magnitude of disturbance light by performing statistical processing on a plurality of sensor outputs obtained from the flame sensor before the ignition attempt, adjusts the reference threshold value by adding the adjustment value to the reference threshold value, and outputs the obtained adjusted threshold value.

In addition, in one example of the configuration of the combustion controlling device according to the invention, the reference threshold value includes a first reference threshold value and a second reference threshold value less than the first reference threshold value, the flame detection adjusting portion outputs a first adjusted threshold value obtained by adjusting the first reference threshold value and a second adjusted threshold value obtained by adjusting the second reference threshold value, the second adjusted threshold value being less than the first adjusted threshold value, and the combustion flame detecting portion detects a presence of a combustion flame in the combustion equipment when the sensor output of the flame sensor obtained during combustion in the combustion equipment is equal to or greater than the first adjusted threshold value and detects an absence of a combustion flame when the sensor output is equal to or less than the second adjusted threshold value.

In addition, according to the invention, there is provided a combustion control method that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the method including a flame detection adjusting step in which a flame detection adjusting portion adjusts a preset reference threshold value based on the sensor output indicating disturbance light obtained from the flame sensor before an ignition attempt in the combustion equipment and outputs an obtained adjusted threshold value; a combustion flame detecting step in which a combustion flame detecting portion detects a presence or an absence of a combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during combustion in the combustion equipment and the adjusted threshold value; and a combustion controlling step in which a combustion controlling portion controls a combustion in the combustion equipment based on a combustion flame detection result obtained in the combustion flame detecting step.

According to the invention, the adjusted threshold value that is larger than the reference threshold value by the adjustment value indicating the magnitude of disturbance light is used to detect a presence or an absence of a combustion flame in the combustion equipment. Therefore, even when disturbance light is potentially present, it is possible to suppress the effect of disturbance light on the detection of a presence or an absence of a combustion flame. Accordingly, the combustion equipment can be controlled safely with respect to disturbance light. In addition, since the threshold value for combustion flame detection is adjusted by the combustion controlling device, the structure of the burner does not need to be changed to prevent disturbance light from entering the flame sensor. With this, it becomes unnecessary to perform a change to existing combustion equipment, such as an exchange of an existing burner, so a significant increase in the cost for measures can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the structure of the combustion controlling device.

FIG. 2 is an explanatory diagram illustrating the calculation of the adjustment value.

FIG. 3 is an explanatory diagram illustrating the adjustment of the threshold values.

FIG. 4 is a flowchart illustrating threshold value adjustment processing.

DETAILED DESCRIPTION

Next, embodiments of the invention will be described with reference to the drawings.

Combustion Controlling Device

First, a combustion controlling device 10 according to the embodiment will be described with reference to FIG. 1. FIG. 1 is a block diagram illustrating the structure of the combustion controlling device.

This combustion controlling device 10 performs combustion control of combustion equipment 30 based on a sensor output S from a flame sensor 20.

The combustion equipment 30 may be general combustion equipment used in industrial furnaces, boilers, air conditioners, kitchen appliances, heat exchangers, and the like and has the function of generating thermal energy by burning fuel in a burner.

The flame sensor 20 detects the light quantity of flame in the burner of the combustion equipment 30, converts the light quantity to electricity, and outputs the electricity to the combustion controlling device 10 as the sensor output S.

The combustion controlling device 10 is provided with a combustion flame detecting portion 11, a flame detection adjusting portion 12, and a combustion controlling portion 13 as main function portions. Each of these function portions may be configured as a controlling circuit comprising ICs or may be achieved in cooperation between a CPU and programs.

The combustion flame detecting portion 11 has the function of obtaining the sensor output S of the flame sensor 20 before an ignition attempt in the combustion equipment 30 and outputting the sensor output S to the flame detection adjusting portion 12 and the function of detecting a presence or an absence of a combustion flame in the combustion equipment 30 based on the sensor output S obtained from the flame sensor 20 during combustion in the combustion equipment 30 and an adjusted threshold value H output from the flame detection adjusting portion 12.

The flame detection adjusting portion 12 has the function of adjusting a preset reference threshold value Hs based on the sensor output S of the flame sensor 20 indicating disturbance light output from the combustion flame detecting portion 11 before an ignition attempt in the combustion equipment 30 and outputting an obtained adjusted threshold value H to the combustion flame detecting portion 11.

Specifically, the flame detection adjusting portion 12 has the function of calculating an adjustment value P indicating the magnitude of disturbance light by performing statistical processing on a plurality of sensor outputs S obtained from the flame sensor 20 before an ignition attempt and the function of adjusting the reference threshold value Hs by adding the adjustment value P to the reference threshold value Hs and outputting the obtained adjusted threshold value H.

FIG. 2 is an explanatory diagram illustrating the calculation of the adjustment value. Here, the period from time T1 to time T2 before an ignition attempt in the combustion equipment 30 is preset as a detection period TP and statistical processing is performed on the plurality of sensor outputs S obtained from the flame sensor 20 in the detection period TP to calculate the adjustment value P indicating the magnitude of disturbance light, such as outside light or stray light. Specific examples of the adjustment value P are the average value, the maximum value, the minimum value, the median value, and the like of the plurality of sensor outputs S. These values only need to be obtained by general statistical processing for calculating these representative values of the plurality of sensor outputs S.

FIG. 3 is an explanatory diagram illustrating the adjustment of the threshold values. The reference threshold value Hs has hysteresis characteristics and includes a first reference threshold value Hs1 (ignition detection level) and a second reference threshold value Hs2 (flame extinction detection level) less than Hs1. The flame detection adjusting portion 12 calculates a first adjusted threshold value H1 (ignition detection level) and a second adjusted threshold value H2 (flame extinction detection level) less than H1 by adding the adjustment value P to Hs1 and Hs2.

With this, the value adjusted by shifting the reference threshold value Hs to be larger by the adjustment value P indicating the magnitude of disturbance light is output to the combustion flame detecting portion 11 as the adjusted threshold value H. When disturbance light is not present, the adjustment value P indicates 0 and the adjusted threshold value H equal to the reference threshold value Hs is output to the combustion flame detecting portion 11.

Accordingly, the combustion flame detecting portion 11 detects a presence (Bon) of a combustion flame in the combustion equipment 30 when the sensor output S of the flame sensor 20 obtained during combustion in the combustion equipment 30 is equal to or greater than the first adjusted threshold value H1 (ignition detection level), detects an absence (Boff) of a combustion flame when the sensor output S is equal to or less than the second adjusted threshold value H2 (flame extinction detection level), and outputs the detected value as a combustion flame detection result B to the combustion controlling portion 13.

The combustion controlling portion 13 has the function of controlling a combustion in the combustion equipment 30 based on the combustion flame detection result B from the combustion flame detecting portion 11 during combustion in the combustion equipment 30. The combustion control performed here is the same as the conventional one. For example, when the combustion flame detection result B indicates a presence (Bon) of a combustion flame, a control signal C for instructing the supply of fuel to the burner is output to the combustion equipment 30. When the combustion flame detection result B indicates an absence (Boff) of a combustion flame, a control signal C for instructing the stopping of the supply of fuel to the burner is output to the combustion equipment 30.

It should be noted that the combustion flame detecting portion 11 and the flame detection adjusting portion 12 may be installed in the flame sensor 20 instead of the combustion controlling device 10. In addition, the adjustment value P may be a value learned by machine learning instead of a value obtained by statistical processing.

Operation of the Embodiment

Next, the operation of the combustion controlling device 10 according to the embodiment will be described with reference to FIG. 4. FIG. 4 is a flowchart illustrating threshold value adjustment processing.

The combustion controlling device 10 makes the threshold value adjustment processing illustrated in FIG. 4 before starting an ignition attempt in the combustion equipment 30.

First, the flame detection adjusting portion 12 obtains the sensor output S of the flame sensor 20 indicating disturbance light output from the combustion flame detecting portion 11 before an ignition attempt in the combustion equipment 30 (step 100). At this time, the sensor output S may be obtained directly from the flame sensor 20 by bypassing the combustion flame detecting portion 11.

Next, the flame detection adjusting portion 12 calculates the adjustment value P indicating the magnitude of disturbance light, such as outside light or stray light, by performing statistical processing on the plurality of sensor outputs S included in the preset detection period TP (step 101).

Next, the flame detection adjusting portion 12 calculates the adjusted threshold values H1 and H2 by adding the adjustment value P to the preset reference threshold values Hs1 and Hs2 (step 102), outputs the obtained adjusted threshold values H1 and H2 to the combustion flame detecting portion 11 (step 103), and ends a series of processes of the threshold value adjustment processing.

Effects of the Embodiment

As described above, in the embodiment, the flame detection adjusting portion 12 adjusts the preset reference threshold value Hs based on the sensor output S indicating disturbance light obtained from the flame sensor 20 before an ignition attempt in the combustion equipment 30 and outputs an obtained adjusted threshold value H, and the combustion flame detecting portion 11 detects a presence or an absence of a combustion flame in the combustion equipment 30 based on the sensor output S obtained from the flame sensor 20 during combustion in the combustion equipment 30 and an adjusted threshold value H.

With this, the adjusted threshold value H larger than the reference threshold value Hs by the adjustment value P indicating the magnitude of disturbance light is used to detect a presence or an absence of a combustion flame in the combustion equipment 30. Therefore, even when disturbance light is potentially present, it is possible to suppress the effect of disturbance light on the detection of a presence or an absence of a combustion flame. Accordingly, the combustion equipment 30 can be controlled safely with respect to disturbance light. In addition, since the threshold value for combustion flame detection is adjusted by the combustion controlling device 10, the structure of the burner does not need to be changed to prevent disturbance light from entering the flame sensor 20. With this, it becomes unnecessary to perform a change to the existing combustion equipment 30, such as an exchange of an existing burner, so a significant increase in the cost for measures can be suppressed.

Extension of the Embodiment

Although the invention has been described above with reference to the embodiment, the invention is not limited to the above embodiment. Various changes understandable to those skilled in the art can be made to the structure and details of the invention within the scope of the invention.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

10: combustion controlling device, 11: combustion flame detecting portion, 12: flame detection adjusting portion, 13: combustion controlling portion, 20: flame sensor, 30: combustion equipment, S: sensor output, H: adjusted threshold value, H1: first adjusted threshold value, H2: second adjusted threshold value, Hs: reference threshold value, Hs1: first reference threshold value, Hs2: second reference threshold value, B: combustion flame detection result, P: adjustment value, C: control signal 

1. A combustion controlling device that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the combustion controlling device comprising: a flame detection adjusting portion that adjusts a preset reference threshold value based on the sensor output obtained from the flame sensor before an ignition attempt indicating disturbance light in the combustion equipment and outputs an obtained adjusted threshold value; a combustion flame detecting portion that detects the presence or the absence of the combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during the combustion in the combustion equipment and the adjusted threshold value; and a combustion controlling portion that controls the combustion in the combustion equipment based on a combustion flame detection result obtained by the combustion flame detecting portion.
 2. The combustion controlling device according to claim 1, wherein the flame detection adjusting portion calculates an adjustment value indicating a magnitude of disturbance light by performing statistical processing on a plurality of sensor outputs obtained from the flame sensor before the ignition attempt, adjusts the preset reference threshold value by adding the adjustment value to the preset reference threshold value, and outputs the obtained adjusted threshold value.
 3. The combustion controlling device according to claim 1, wherein the preset reference threshold value includes a first reference threshold value and a second reference threshold value less than the first reference threshold value, the flame detection adjusting portion outputs a first adjusted threshold value obtained by adjusting the first reference threshold value and a second adjusted threshold value obtained by adjusting the second reference threshold value, the second adjusted threshold value being less than the first adjusted threshold value, and the combustion flame detecting portion detects the presence of the combustion flame in the combustion equipment when the sensor output of the flame sensor obtained during the combustion in the combustion equipment is equal to or greater than the first adjusted threshold value and detects the absence of the combustion flame when the sensor output is equal to or less than the second adjusted threshold value.
 4. A combustion control method that controls a combustion in combustion equipment based on a presence or an absence of a combustion flame in the combustion equipment detected from a sensor output of a flame sensor, the method comprising: adjusting, by a flame detection adjusting portion, a preset reference threshold value based on the sensor output obtained from the flame sensor before an ignition attempt indicating disturbance light in the combustion equipment and outputting an obtained adjusted threshold value; detecting, by a combustion flame detecting portion, the presence or the absence of the combustion flame in the combustion equipment based on the sensor output obtained from the flame sensor during the combustion in the combustion equipment and the adjusted threshold value; and controlling, by a combustion controlling portion, the combustion in the combustion equipment based on a combustion flame detection result obtained in the combustion flame detecting step. 